Address range substitution sed

Extract value from key=value file sed -n 's/^DB_HOST=//p' .env Substitute first match per line sed 's/foo/bar/' file.txt Substitute all matches (global) sed 's/foo/bar/g' file.txt In-place edit sed -i 's/old/new/g' config.cfg In-place edit with backup sed -i.bak 's/old/new/g' file.txt